A magnetic fluid seal has conventionally been known as a long-lived and clean high-performance seal. This magnetic fluid seal is widely used during a manufacturing process without maintenance of semiconductors or liquid crystals requiring a clean atmosphere, especially its various coating and etching steps.
The magnetic fluid seal uses a sealing film made of a magnetic fluid, and respectively formed between magnetic pole member held inside an outer cylinder member fixed to a housing of a fluid machine and a rotating shaft to seal a gap between the housing and the rotating shaft of the fluid machine.
The sealing film is formed in the magnetic fluid seal. If the fluid sealed to the fluid machine, for example, is a high-temperature gas, heat conducts from the high-temperature gas to the outer cylinder member, and a temperature of the magnetic pole member within the outer cylinder member gradually increases, and the temperature of the sealing film made of the magnetic fluid consequently increases, and when this temperature excessively increases, a base liquid of the magnetic fluid vaporizes, and sealability of the sealing film is no longer maintained. In consideration of this influence of heat, there is proposed such a structure that a cooling fluid passage is formed on an outer peripheral surface of the outer cylinder member which holds two magnetic pole members aligned in the axial direction. The cooling fluid passage is substantially at a center in the axial direction of the magnetic pole members (refer to Patent Citation 1).
The magnetic pole members positioned on right and left sides of the cooling flow passage are cooled by allowing a cooling water to flow into the cooling flow passage. The heat conducted from the high-temperature gas to the outer cylinder member is intercepted before the conduction via the magnetic pole member to the sealing film by the cooled magnetic pole members, the increase in the temperature of the sealing film can thus be suppressed, and the vaporization of the base liquid of the magnetic fluid can be suppressed, thereby increasing the life of the sealing film.
Moreover, there is proposed such a structure that heat radiation plates constructed by multiple recessed grooves are formed on an outer peripheral surface of an outer cylinder member which holds two magnetic pole members aligned in the axial direction. The heat radiation plates are positioned substantially at a center in the axial direction of the magnetic pole members (refer to Patent Citation 2).
As a result, the heat of the magnetic pole member or the sealing film disposed within the outer cylinder member can be released via the outer cylinder member by the heat radiation plates having large surface areas, thereby suppressing a temperature increase in the sealing film.